Information equipment includes apparatus for recording and reading information, one of which is a magnetic disk drive.
A typical structure of conventional magnetic disk drive will be described with reference to FIG. 20 which is a sectional view thereof. A spindle motor for rotating a magnetic disk 1302, on which magnetic information is to be recorded and stored, comprises bearings 1303 and 1305 disposed in the center thereof in axially stacked relation to each other, a member 1308 formed integrally with a shaft which rotates in combination with inner rings of the bearings, a magnet 1307 attached to the member 1308, and a coil 1306 disposed on a base 1309. The magnetic disk 1302 is fixed to the member 1308 by means of a fixing member 1310.
An actuator for positioning a slider on which mounted is a magnetic head which moves on a surface of the magnetic disk 1302 so as to record and/or reproduce magnetic information, comprises a shaft 1313 press-fitted in a base 1301, two bearings 1312 and 1314 fitted on the shaft in series, a carriage 1315 oscillating about the shaft, a magnet 1316 for applying a magnetic field to the carriage, and a load arm 1311 supporting the slider having the magnetic head mounted thereon and attached to the carriage.
There is provided a cover 1317 which encloses the spindle motor, the actuator and so on while being kept in airtight relation to the base on which the spindle motor and the actuator are fixed. A control circuit for controlling the magnetic disk drive is provided on a substrate 1318 disposed below the base, and a connector 1319 used for the power supply from external circuit and for input/output of information is connected to the substrate 1318.
In such conventional magnetic disk drive, the spindle motor and the actuator each use two bearings arranged on the shaft in series, and therefore there is a limit in making the magnetic disk drive thinner.
As for the structure for making the magnetic disk drive thinner, Japanese Patent Unexamined Publication No. 3-169250 discloses one in which two bearings are arranged coaxially in one plane in such a manner that a second bearing is disposed between an outer peripheral surface of a hub and an inner peripheral surface of a housing, these outer and inner peripheral surfaces facing to each other.